/Engine/Plugins/Runtime/GeometryProcessing/Source/GeometryAlgorithms/Public/Arrangement2d.h
Triangles: Output triangles (as indices into Graph vertices) SkippedEdges: Output indices of edges that the algorithm failed to insert BoundaryEdgeGroupID: ID of edges corresponding to a boundary; if we have a closed loop of these boundary edges on output triangulation, will discard triangles outside this return: false if triangulation algo knows it failed (note Triangles may still have some triangulation of the input in this case; for example it may just be missing some required edges)
bool AttemptTriangulate ( [TArray](API\Runtime\Core\Containers\TArray)< [FIndex3i](API\Runtime\GeometryCore\FIndex3i) > & Triangles, [TArray](API\Runtime\Core\Containers\TArray)< int32 > & SkippedEdges, int32 BoundaryEdgeGroupID )